This invention relates to the field of image quality and specifically image permanence of a toner image produced by electrophotographic methods. The apparatus and method of the present invention are directed to an analysis of the permanence of the image and comprise an apparatus and method designed to effectively and reproducibly test the effect of controlled abrasion on a test image.
The production of images using a toner on plain paper by electrophotographic means is common and well known. As printers employing electrophotography increase in speed and image quality, they are found in environments outside the realm of office copiers. These other environments often employ finishing equipment, such as folders, to make a finished product including the images on paper produced by the printer. These devices require means to move and control the position of the printed sheets relative to each other.
To achieve this control, the finishing equipment must come in contact with the image-bearing sheets. In some equipment this contact for handling of the image can abrade the image. This abrasion can manifest itself in several ways, but in general it is a smudge on another page (rub-off) and detracts from the overall quality of the image of a second sheet.
Attempts to quantify the amount of abrasion or rub-off of the image have resulted in various testing methods and apparatus. The apparatus has consisted of a moveable platen, a friction motor drive and weights used together to provide a controllable means to generate rub-off.
The prior art apparatus basically supported a test sheet of a material to be evaluated on a platen, face up, with the leading edge of the test sheet extending beyond the front end of the platen. A standard material receiver sheet was then placed over the test sheet with its leading edge aligned with the front edge of the platen. A known weight providing pressure similar to the pressures used in finishing equipment was then placed on top of the papers completing the stack. The location of the weight was just behind the front edge of the platen. The test sheet was then pulled out from under the receiving sheet. The area where the weight rests on both sheets (test area) was then analyzed for toner residue from the test sheet. The amount of toner in the test area on the receiver sheet has been shown to correlate with the subjective impressions of the amount of rub-off from copies produced by a given system.
Other abrasion testers are known to the art. The Sutherland Rub Tester and the GAT V Abrasion Tester are devices that follow ASTM standards for abrasion of printing inks.
These tests are identified by ASTM Designations D-5264-92 and D-5181-91. These procedures, however, are considered to be much more aggressive procedures and are not considered suitable for the rub-off levels encountered in current toner-based systems. Previously used tests have been very susceptible to the subjective interpretation of the test operator.
Accordingly, since the reduction and control of rub-off from copies produced from modern copy machines is of increasing interest, a continuing effort has been directed to developing a more reproducible test method which is not susceptible to subjective interpretation by the test operator.
According to the present invention, rub-off from an image-bearing substrate is tested by positioning a test substrate having an image-bearing side bearing a plurality of images and a receiver substrate in contact at a test area at a selected pressure; moving the test substrate relative to the receiver substrate a selected distance through the test area; and, determining the relative amount of rub-off in the test area on the receiver by use of a calibrated scanner.
The present invention further comprises a method for measuring rub-off from an image-bearing substrate, the method comprising: positioning a test substrate having a first and a second side with its first side bearing a plurality of images on a flat surface with its second side supported by the flat surface; positioning a receiver substrate over the test substrate and restricting movement of the receiver substrate relative to the flat surface; positioning a selected weight above the receiver substrate at a selected location so that the weight urges the receiver substrate into engagement with the test substrate in a test area; moving the test substrate a selected distance relative to the receiver substrate through the test area; and, determining the relative amount of rub-off in the test area on the receiver substrate by use of a calibrated scanner.
The present invention further comprises a method of measuring rub-off from an image-bearing substrate, the method comprising: positioning a receiver substrate having a first and a second side on a flat surface with one of its sides supported by the flat surface; positioning a test substrate having a first and a second side with its first side bearing a plurality of images over the receiver substrate with its first side supported on the receiver substrate; restricting movement of the receiver substrate relative to the flat surface; positioning a selected weight above the test substrate at a selected location so that the weight urges the test substrate into engagement with the receiver substrate in a test area; moving the test substrate a selected distance relative to the receiver substrate through the test area; and, determining the relative amount of rub-off in the test area on the receiver substrate by use of a calibrated scanner.
The present invention also comprises an apparatus for measuring rub-off from an image-bearing substrate, the apparatus comprising: a flat surface having a first and a second end, a length and adapted to support a first substrate with one of its ends extending beyond the first end of the flat surface; a restrainer for preventing movement of a second substrate along the length of the flat surface; a pressure pad adapted to impose a selected pressure on the first substrate and the second substrate in a test area; a puller adapted to pull the first substrate a selected distance through the test area relative to the second substrate; a calibrated scanner; and, a computer program for converting the scanner results into a numerical test result.